Add checked_cast to size_t conversion in multibuffer_data_source.cc

media/blink/multibuffer_data_source.cc

Index: media/blink/multibuffer_data_source.cc
diff --git a/media/blink/multibuffer_data_source.cc b/media/blink/multibuffer_data_source.cc
index 3eb6e51459f132aa1e9713921ff55173e743f63b..91d61231eb86a3f643c1e0b048c8ba38b156a861 100644
--- a/media/blink/multibuffer_data_source.cc
+++ b/media/blink/multibuffer_data_source.cc
@@ -10,6 +10,7 @@
 #include "base/callback_helpers.h"
 #include "base/location.h"
 #include "base/macros.h"
+#include "base/numerics/safe_conversions.h"
 #include "base/single_thread_task_runner.h"
 #include "media/base/media_log.h"
 #include "media/blink/buffered_data_source_host_impl.h"
@@ -335,7 +336,7 @@ void MultibufferDataSource::OnBufferingHaveEnough(bool always_cancel) {
 
 int64_t MultibufferDataSource::GetMemoryUsage() const {
   // TODO(hubbe): Make more accurate when url_data_ is shared.
-  return url_data_->CachedSize()
+  return base::checked_cast<int64_t>(url_data_->CachedSize())

[brucedawson, 2017/02/02 22:22:52]

Why do we need a checked cast for converting to a larger size? The cast makes
sense, I'm only curious about why a checked_cast was felt to be necessary.

But, checked_cast is probably smart enough to be free in this case so it doesn't
really matter.

[jrummell, 2017/02/03 01:35:40]

My understanding is that on some systems size_t is 64 bits, so a simple
conversion is bad. I thought Chromium encouraged use of the helpers, as past
CL's have had comments that I should use them.

          << url_data_->multibuffer()->block_size_shift();
 }